Excavating machines, such as tractor loader backhoes (TLBs), are versatile in their ability to load material by virtue of implements, such as buckets, disposed at each end of the tractor. The conventional backhoe includes a boom mounted on the rear of a tractor carrying a pivotal bucket for the digging operation. The boom is mounted on a frame about a horizontal pivot axis between raised and lowered positions by a fluid ram joining the frame and the boom. When the backhoe is not in operation, it is typically desirable to bring the boom to a raised position where it engages a latching mechanism and is maintained in the raised latched position. Maintaining the boom in the latched position moves the center of gravity of the backhoe forward, which is desirable for improved operation of the machine.
However, there are problems associated with bringing the boom to the latched position in a smooth fashion. If the operator has not sufficiently slowed the rate at which the boom 14 is being raised as the boom approaches the raised position (FIG. 3) from a lowered position (FIG. 1), upon the boom 14 achieving the raised position, boom 14 will impact frame 20. The magnitude of such impact can be significant, due to the large combined weight of the backhoe 12, especially when the backhoe is traveling at significant speed toward the cab of the machine 10. As shown in FIG. 4, a bumper 44, typically comprised of high density rubber or the like, is the only buffer between contacting surfaces of frame 20 and boom 14. Bumper 44 provides little impact absorption, the resulting impact between the boom 14 and frame 20 subjecting the machine 10 to a sudden and violent jarring effect that can not only damage the machine 10, but similarly subjects the operator to the jarring effect.
Once the boom 14 achieves the raised position, a latching device 76 can be actuated to place the boom in a latched position (see FIGS. 4 and 6). In the latched position, the bumper 44 is compressed between the boom 14 and the frame 20. However, due to the large mass of the backhoe 12, while the machine is driven or is moved between work sites, road imperfections cause the backhoe 12 to “bounce” in the latched position, imparting shock loads into the machine structure. As bumper 44 wears through time and usage, the movement of the backhoe 12 with respect to machine 10 increases, similarly increasing the magnitude of these shock loads and adversely affecting the overall travel or “roading” quality of the machine.
Further, certain backhoe operations, such as when material is to be loaded into a truck and the boom achieves substantially raised positions, it possible for the boom to inadvertently latch with the latching device. Such inadvertent latching requires the operator to unlatch the boom before further work can be performed, which is disruptive and inefficient.
What is needed is a system that helps dissipate the jarring impacts between the boom and the frame, both while achieving a raised position of the boom and while the machine is operating with the backhoe in the latched position, but additionally, substantially preventing inadvertent achievement of the latching position of the boom.